This invention is directed to compounds which are reaction products of alpha-aminomethylene phosphonic acids and epoxy compounds and to their use in coating compositions.
U.S. Pat. No. 4,621,112 is directed to the use of an organic ester of orthophosphoric acid, which ester is the reaction product as specified of a compound containing a --O--PO.sub.3 H.sub.2 group with a compound containing an epoxide group, to help prevent the evolution of gas (alternately referred to in the present application as "gassing") by the reaction of metallic pigment with the aqueous phase of a waterborne coating composition. While the use of such organic esters of orthophosphoric acid may help meet the object of providing an antigassing additive for such waterborne coating compositions, a number of disadvantages have been found with respect to such use. For example, it has been found that dry films produced from waterborne coating compositions which incorporate such art known compounds tend to be deficient in humidity resistance. Moreover, their effectiveness as antigassing agents is not entirely satisfactory.
The present invention is directed to a new class of compounds which not only reduce or prevent gassing of waterborne coating compositions containing metallic pigment better than the aforesaid art known organic esters of orthophosphoric acid, but, among other advantages, do not disadvantageously hurt humidity resistance of dry films produced therefrom compared to such art known organic esters of orthophosphoric acid. Moreover, the present invention is also directed to the use of this new class of compounds in organic solvent-borne coating compositions containing organic coloring pigment to improve the color stability of such solvent-borne coating compositions. Additionally, the present invention is directed to the use of this new class of compounds in powder coatings to improve the dispersibility of pigment therein. These and other objects of the invention will become apparent to the reader infra.